Impact detection system

ABSTRACT

An impact detection system provides a means of sensing, monitoring and recording impact events on an impact surface using at least one sensor that is incorporated into the impact surface. The sensor(s) can be integral with, attached to or located behind various types of impact surface including various types of garments that can be worn by an individual or on composite materials such as an aircraft fuselage for example. The impact detection system includes a portable impact detection device electrically connected to the sensor(s) and is used to detect ballistic or non-ballistic type impacts on the impact surface. The portable impact detection device processes the impact data detected by the sensor(s) and stores the data for analysis at a later time or outputs the data to a third party system for review and/or analysis.

This is a national stage of PCT/NZ07/000,208 filed Aug. 7, 2007 andpublished in English, which has a priority of New Zealand no. 551819filed Dec. 4, 2006, hereby incorporated by reference.

FIELD OF INVENTION

The present invention relates to an impact detection system. Inparticular, although not exclusively, the impact detection system iscapable of measuring a number of ballistic or non-ballistic typefeatures, such as absorption energy for example, as a result of animpact on a body.

BACKGROUND TO THE INVENTION

A number of systems have been used in the past to detect and/or monitorthe effects of an impact from an object, for example a projectile on abody. In a laboratory environment plastina clay has typically been usedwhen trialling or testing the ballistic type effects of an impact from aprojectile, such as a bullet for example, on a body whereby the plastinaclay simulates body composition. Using this type of system it is notpossible to measure the actual back face velocity of an armour plate forexample that is placed in front of the plastina clay. Therefore,measurements relating to the impact of the projectile on the body areinferred by indirect methods as a result of an analysis undertaken ondeformation of the plastina clay.

Detecting the penetration of impacts on a body may also be measured byusing a mesh fabric incorporating fibre optics placed on armour worn bya user. When a fibre is broken, it is assumed to be caused by apenetrating impact. However, this type of system is generally veryfragile and cannot be used to accurately determine a ballistic impactfrom a rip or tear in the armour fabric caused by other sources.

Other ballistic impact detection systems incorporate peizo electric filmsensor elements attached to body armour for example. The peizo filmsensors detect acoustic vibration patterns caused by impacts and convertthem into a voltage. The voltage is passed through a circuit whichdetermines if the impact has the frequency and amplitude characteristicsthat have become associated with typical impacts that cause injuries.The voltage output from the peizo film sensors feed a battery poweredanalogue or digit circuit which has to be carried by the user orcombatant. The circuitry is used to isolate the high energy acousticsignatures produced by ballistic impacts and discerns the approximateimpact location on the body. This type of system requires a considerableamount of signal processing and filtering of the acoustic signatures inorder to discriminate impact signature information from noise forexample in order to provide useable impact data output.

There is therefore a need for an impact detection system for detectingand monitoring the effects of impacts on a body and in particular butnot exclusively, impacts that might cause injury.

In this specification if reference has been made to patentspecifications, other external documents, or other sources ofinformation, this is generally for the purpose of providing a contextfor discussing the features of the invention. Unless it is specificallystated otherwise, reference to such external documents is not to beconstrued as an admission that such documents, or such sources ofinformation, in any jurisdiction, are prior art or form part of thecommon general knowledge in the art.

It is an object of the present invention to provide improved impactdetection system for detecting and measuring impact relatedcharacteristics on a body, or at least to provide industry or the publicwith a useful choice.

SUMMARY OF THE INVENTION

In a first aspect, the present invention consists in an impact detectionsystem for detecting and measuring impact related characteristics on abody comprising:

an impact surface,

at least one fabric compression sensor having an electricalcharacteristic attached to or integral with said impact surface andadapted to detect an impact event on said body, and

an impact detection device electrically connected to said at least onefabric compression sensor, said impact detection device including:

-   -   a detection circuit for detecting changes in said electrical        characteristic produced due to an impact on said impact surface;    -   a processing circuit for processing said detected changes in        said electrical characteristic into a digital data format        representative of an impact characteristic on said impact        surface.

Preferably, said impact detection device also includes a user interfacefor outputting said digital data to a visual and/or audible outputdevice for analysis and/or review by an individual.

Preferably, said impact detection device also includes a storage devicefor storing said digital data and a communication system forcommunicating said digital data to a third party system for analysisand/or storage of said digital data.

Preferably, said impact detection system is a portable lightweightdevice.

Preferably, said impact detection device is activated when an impactevent is detected on said impact surface.

Preferably said impact related characteristics on said body include aballistic impact or a non-ballistic impact.

Preferably, said impact surface is segmented to provide a plurality ofdetection zones wherein each of said plurality of detection zones has atleast one fabric compression sensor attached to, integral with, locatedbehind or in front of said impact surface and electrically connected tosaid impact detection device.

Preferably, said at least one fabric compression sensor is used todetect said impact event caused by an externally applied force on saidimpact surface.

Preferably, said impact detection device is driven by an AC signalhaving a high output resistance.

Preferably, said at least one fabric compression sensor is a capacitivefabric compression sensor formed by at least two layers of conductivefabric having a compressible non-conductive material between each ofsaid layers of conductive fabric.

Preferably, said compressible non-conductive material deforms orcompresses when said impact surface is deformed due to said impactevent.

Preferably, said at least one fabric compression sensor includes aninner conductive layer surrounded by an outer conductive fabric layerseparated by a layer of said compressible non-conductive material.

Preferably, said outer conductive layer is coupled to an AC groundwithin said impact detection device and said inner conductive layer iscoupled to said AC signal having a high output resistance such that saidfabric compression sensor has output characteristics equivalent to thoseprovided by a variable capacitor.

Preferably, said impact event causes said AC signal to change inamplitude due to a change in a capacitive coupling between said innerconductive layer and said outer conductive layer.

Preferably, said change in capacitive coupling is caused by a change ina separation distance between said inner conductive layer and said outerconductive layer due to said compressible non-conductive layer beingdeformed and/or compressed as a result of said impact event.

Preferably, said processing circuit samples the amplitude of said ACsignal to generate a digital impact event related waveform and datarepresentative of said impact event for storage in said storage devicewithin said impact detection device and/or for output to a third partysystem.

Preferably, said inner conductive layer is formed from a stretchable andflexible fabric material.

Alternatively, said inner conductive layer is formed from a metallisedcloth.

Alternatively, said inner conductive layer is formed from a metallicmaterial

Preferably, said outer conductive layer is formed from a stretchable andflexible fabric material.

Alternatively, said outer conductive layer is formed from a metallisedcloth.

Alternatively, said outer conductive layer is formed from a metallicmaterial.

Preferably, said compressible non-conductive layer is formed from aclosed cell foam type of material.

Preferably, said impact surface is selectable from the list comprising:a bullet proof vest, helmet, clothing, body armour, ceramic armour, anindividual's body, a body harness or strap and composite surfaces.

Preferably, said impact surface is capable of incorporating at least oneor more alternative type of sensor including any one or more selectedfrom a list comprising: a pressure sensor, temperature sensor, heartrate sensor, respiration sensor, direction sensor or movement sensor.

Preferably, said communications system includes a communications port.

Alternatively, said communications system includes a wirelesstransmitter.

Preferably, said communications port provides a user interface betweensaid third party system and said impact detection device enabling a userto use said third party system to download said digital impact relateddata from said impact detection device to said third party system.

Alternatively, said wireless transmitter provides a user interfacebetween said third party system and said impact detection deviceenabling a user to use said third party system to download said digitalimpact related data from said impact detection device to said thirdparty system.

Preferably, said at least one fabric compression sensor is integral saidimpact surface.

Preferably, said electrical connection is made by at least oneconductive thread.

Preferably, said impact detection device is a low power battery drivendevice.

In a second aspect the present invention consists in garment worn by auser and used to detect and measure the effects of an impact on a usercomprising:

at least one fabric compression sensor integral with said garment,

an impact detection device electrically connected to said at least onefabric compression sensor, and

a detecting circuit capable of detecting changes in said electricalcharacteristic caused by an impact event on said garment, said impactdetection device including:

-   -   a processing circuit for processing the changes in said        electrical characteristic into a digital data format        representative of an impact characteristic on said garment.

Preferably, said impact detection device includes a user interface foroutputting said digital data to a visual and/or audible output devicefor analysis and/or review by an individual.

Preferably, said impact detection device also includes a storage devicefor storing said digital data, and a communication system forcommunicating said digital data to a third party system for analysisand/or storage of said digital data.

Preferably, said impact detection device is a portable lightweightdevice.

Preferably, said impact detection device is activated when an impactevent is detected on said garment.

Preferably, said impact related characteristics on said user include aballistic impact or a non-ballistic impact.

Preferably, said garment is segmented to provide a plurality ofdetection zones wherein each of said plurality of detection zones has atleast one fabric compression sensor integral with, attached to orlocated in front or behind said garment and electrically connected tosaid impact detection device.

Preferably, said at least one fabric compression sensor is used todetect said impact event caused by an externally applied force on saidgarment.

Preferably, said impact detection device is driven by an AC signalhaving a high output resistance.

Preferably, said at least one fabric compression sensor is a capacitivefabric compression sensor formed by at least two layers of conductivefabric having a compressible non-conductive material between each ofsaid layers of conductive fabric.

Preferably, said compressible non-conductive material deforms orcompresses when said impact surface is deformed due to said impactevent.

Preferably, said at least one fabric compression sensor includes aninner conductive layer surrounded by an outer conductive fabric layerseparated by a layer of said compressible non-conductive material.

Preferably, said outer conductive layer is coupled to an AC groundwithin said impact detection device and said inner conductive layer iscoupled to said AC signal having a high output resistance such that saidfabric compression sensor has output characteristics equivalent to thoseprovided by a variable capacitor.

Preferably, said impact event causes said AC signal to change inamplitude due to a change in a capacitive coupling between said innerconductive layer and said outer conductive layer.

Preferably, said change in capacitive coupling is caused by a change ina separation distance between said inner conductive layer and said outerconductive layer due to said compressible non-conductive layer beingdeformed and/or compressed as a result of said impact event.

Preferably, said processing circuit samples the amplitude of said ACsignal to generate a digital impact event related waveform and datarepresentative of said impact event for storage in said storage devicewithin said impact detection device and/or for output to a third partysystem.

Preferably, said inner conductive layer is formed from a stretchable andflexible fabric material.

Alternatively, said inner conductive layer is formed from a metallisedcloth.

Alternatively, said inner conductive layer is formed from a metallicmaterial.

Preferably, said outer conductive layer is formed from a stretchable andflexible fabric material.

Alternatively, said outer conductive layer is formed from a metallisedcloth.

Alternatively, said outer conductive layer is formed from a metallicmaterial.

Preferably, said compressible non-conductive layer is formed from aclosed cell foam type of material.

Preferably, said garment is selectable from the list comprising: abullet proof vest, helmet, clothing, body armour, a body harness orstrap and ceramic armour.

Preferably, said garment is capable of incorporating at least one ormore alternative sensor types including any one or more selected from alist comprising: a pressure sensor, temperature sensor, heart ratesensor, respiration sensor, direction sensor or movement sensor.

Preferably, said communications system includes a communications port.

Alternatively, said communications system includes a wirelesstransmitter.

Preferably, said communications port provides a user interface betweensaid third party system and said impact detection device enabling a userto use said third party system to download said digital impact relateddata from said impact detection device to said third party system.

Alternatively, said wireless transmitter provides a user interfacebetween said third party system and said impact detection deviceenabling a user to use said third party system to download said digitalimpact related data from said impact detection device to said thirdparty system.

Preferably, said electrical connection is made by at least oneconductive thread.

Preferably, said impact detection device is a low power battery drivendevice.

In a third aspect, the present invention consists in a method ofdetecting and measuring impact related characteristic on a body using animpact detection device comprising:

at least one fabric compression sensor having an electricalcharacteristic, and

an impact detection circuit electrically connecting said at least onefabric compression sensor, said method comprising the steps of:

-   -   activating said impact detection circuit on detecting a change        in said electrical characteristic caused by an impact on said        body,    -   processing said changes in said electrical characteristic into a        digital data format representative of an impact type        characteristic on said body. And    -   storing said digital data in a storage device within said impact        detection device, and communicating said digital data to a third        party system for analysis and/or storage of said digital data

Preferably, said step of processing said changes in said electricalcharacteristic further includes the steps of outputting said digitaldata to a visual and/or audio device via a user interface.

Preferably, said step of processing said changes in said electricalcharacteristic includes measuring changes in a capacitive coupling ofsaid least one fabric compression sensor as a result of an impact onsaid body by an externally applied force.

Preferably, said step of communicating includes sending said digitaldata from said storage device to said third party system via acommunications port.

Preferably, said step of communicating includes transmitting saiddigital data from said storage device to said third party system via awireless transmitter.

To those skilled in the art to which the invention relates, many changesin construction and widely differing embodiments and applications of theinvention will suggest themselves without departing from the scope ofthe invention as defined in the appended claims. The disclosures and thedescriptions herein are purely illustrative and are not intended to bein any sense limiting.

The term ‘comprising’ as used in this specification and claims means‘consisting at least in part of’, that is to say when interpretingstatements in this specification and claims which include that term, thefeatures, prefaced by that term in each statement, all need to bepresent but other features can also be present.

The invention consists in the foregoing and also envisages constructionsof which the following gives examples only.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to theaccompanying drawings in which:

FIG. 1 is a diagram of the impact detection system of the presentinvention.

FIG. 2 is diagram of the impact detection system of FIG. 1 showing theconstructions of the capacitive fabric compression sensor.

FIG. 3 is a diagram of the system of FIG. 1 showing the effects of animpact on the capacitive fabric compression sensor.

FIG. 4 is a block diagram of the electronic sensing system of FIG. 1.

FIG. 5 is a graph of the impact detected by the electronic circuitryshowing the back face velocity of the impact and subsequently bound.

FIG. 6 is an electrical block diagram of the electronic sensing systemof FIG. 1.

FIG. 7 is an alternative electrical block diagram of the electronicsensing system of FIG. 1.

FIG. 8 is a diagram of sections of capacitive fabric compression sensorsincorporated within an item of clothing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The detection and measurement of ballistic and/or non-ballistic impactson a soldier's body for example would prove invaluable in the ability toincrease the survivability of a soldier in a battle field situation. Asan example, an impact detection system may facilitate a more rapidresponse by medics depending on the output generated from the detectionsystem worn by a soldier as a result of an impact being detected.

The impact detection system of the present invention can be used onvarious types of impact surfaces such as body armour including a bulletproof vest, battle fatigues, a uniform, a body harness or strap, helmetor other garments designed for the body including underwear.Alternatively, the system can be used to detect impacts on other typesof composite materials such as those found on an aircraft fuselage, boathull or armour on a tank for example. These impacts can be of aballistic or non-ballistic nature. The system provides a means ofsensing, monitoring and recording impact events on an impact surfaceusing at least one sensor that is incorporated into the impact surface.Alternatively, the sensor(s) are attached to, integral with, or can belocated behind or in front of the impact surface. Furthermore, thesensor(s) can be integral with patches used to adhere to the user's bodyin desires positions. The impact detection system is capable ofdetecting an impact(s) on a body and enabling a number of ballistic typefeatures such as back face velocity, impact force and absorption energyto be determined and analysed for example. Whilst a number of measuredballistics type features have been mentioned these are in no waylimiting as the sensing system can be used in a wide variety ofenvironments and for a wide variety of purposes including non-ballistictype impacts.

Capacitive Fabric Compression Sensors

A preferred embodiment of the impact detection system of the presentinvention is shown in FIG. 1. A capacitive fabric compression sensor 1is attached to, integral with or located behind or in front of an impactsurface 2 such as a layer of body armour. Whilst only one capacitivecompression sensor 1 is shown, a number of capacitive compressionsensors (not shown) may be attached to the impact layer 2 to provide anumber of detection zones each of which are electrically connected tothe impact detection device 3. The capacitive compression sensor(s) 1can be attached to the impact surface 2 using an attachment mechanismsuch as Velcro™ attachments, press-fit or snap-fit type attachments,compression connections such as crimping or soldering or alternativelythe use of conductive adhesives and glues. Alternatively, if the impactlayer 2 is a wearable garment such as battle fatigues or other form ofclothing, the capacitive compression sensor(s) 1 can be integrated withthe garment fabric during manufacture of the garment. An electronicimpact detection device 3 is electrically connected or interfaced to thecapacitive compression sensor(s) 1 via electrical connections 9, 10 suchas conductive yarn or direct connection at the sensor location. Asimpact detection device 3 is very compact and small, it is preferablethat the impact detection device 3 is portable and incorporated and wornas part of on the user's clothing. Alternatively, the impact detectiondevice 3 can be fitted to a user's belt or enclosed within a pouch orpocket for example. This enables the impact detection device 3 to belocated a short distance from the capacitive compression sensor(s) 1 andthus protecting the device 3 from potential impact damage.

Each capacitive fabric compression sensor 1 includes an inner centrallayer of conductive material 6 such as metallised cloth, metallicmaterial or a stretchable and flexible fabric material that issurrounded by a layer of deformable or compressible non-conductive layerof material 7 such as closed cell foam or other compressible materialthat has repeatable mechanical properties as shown in FIG. 2. The innercentral layer 6 and compressible non-conductive layer 7 are thenenclosed within an outer layer of conductive material 8 such asmetallised cloth, metallic material or a stretchable and flexible fabricmaterial. The inner conductive layer 6 is electrically connected by aconductive thread 9 to the impact detection device 3 to provide animpact sensing signal input to the impact detection device 3 whilst theouter conductive layer 8 is electrically connected using a conductivethread 10, to signal ground via the impact detection device 3. The outerconductive layer includes an electrical isolation region 11 that is usedto provide electrical isolation between the outer conductive layer 8 andthe inner conductive layer electrical connection 9 extending through theouter conductive layer wall 8. As the outer conductive layer 8 isreferenced to the electronics signal ground via conductive thread 10,this type of electrical configuration does not tend to be effected byinterference such as noise external to the capacitive compressionsensor(s) 1. The layered configuration of the capacitive compressionsensor 1 enables the capacitance between the inner conductive layer 6and the outer conductive layer 8 to be detected and measured by theimpact detection device 3. The capacitance changes as a result ofcompressible non-conductive layer 7 being compressed or deformed due toan impact from a projectile 12 for example, travelling in the directionof the arrow 12 a on the impact surface 2 as shown in FIG. 3.

Effects of Impact

The capacitive fabric compression sensor(s) 1 is attached to an impactsurface 2 such as an armoured plate as shown in FIGS. 1 to 3. Aprojectile 12 is fired in the direction of the arrow 12 a at the impactsurface 2 causing the impact surface 2 to be deformed and an indentcreated in the impact surface 2 as a result of the projectile 12striking the impact surface 2 as shown in FIG. 3. The deformation orindentation of the impact surface 2 causes at least the outer conductivelayer 8 of the capacitive compression sensor 1 to also deform. Thiscauses the compressible non-conductive layer 7 to be compressed therebyreducing the spatial distance between the outer and inner conductivelayers 6, 8 respectively. Therefore, due to the electrical connection 9,10 of the inner and outer conductive layers 6, 8, the capacitancebetween the inner and outer layers 6, 8 changes as the compressiblenon-conductive layer 7 is compressed.

As the outer conductive layer 8 is conductive and referenced toelectrical ground via conductive thread 10, there is little or no effecton the ability to detect capacitive changes between the two conductivelayers 6, 8 as a result of outside interference on the capacitivecompression sensor 1. Changes in the capacitive coupling between theinner 6 and outer 8 conductive layers can be detected and measured bythe impact sensing and processing device. This data is used to determinethe change in distance between each of the conductive layers 6, 8. Usingthe change in distance between the conductive layers 6, 8, it ispossible to determine impact ballistics data such as the speed andenergy of an impact from the projectile 12 for example, on the armourplate or other impact surface 2. The measurement of the energy absorbedby the impact surface 2 is of particular importance particularly whenused to design and develop more effective body armour for example.

Impact Detection Device

Each capacitive fabric compression sensor(s) 1 is attached to the impactsurface 2 and is electrically connected to the impact detection device 3by one or more conductive threads 9, 10. The impact detection device 3is a small portable device that can be discretely concealed on theuser's body or within the user's clothing for example. Whilst it ispreferable to interface the capacitive fabric compression sensor(s) 1 tothe impact detection device 3 using conductive thread type electricalconnections 9, 10, other forms of electrical connections can be made forexample, standard type cable or wire. It is therefore possible toposition the impact detection device 3 in a position such that it isisolated from the capacitive fabric compression sensor(s) 1 and theimpact surface 2 and as such, less likely to be affected or damaged byany impacts from a projectile 12 on the impact surface 3.

The electronic impact detection device 3 is capable of collecting andoutputting data to a visual display device and/or and audible device viaa user interface and/or storing impact data in storage device such asmemory 14 within the impact detection device 3. The stored data can bedownloaded to a third party system for impact data analysis via acommunications system 20 such as a communications port serial interfacethat is integral with the impact detection device. Alternatively, theimpact detection device may incorporate a wireless transmitter that canbe used to download the stored impact data to a remote third partysystem. Alternatively, once an impact is detected, the impact data canbe transmitted in real time to a remote third party system at a remotelocation for analysis to be undertaken on the impact data.

The impact detection device 3 is shown in FIG. 4 and is only triggeredas a result of an impact event being detected. That is, when thedistance between the inner and outer conductive layers 6, 8 changes dueto the non-conductive layer 7 being deformed or compressed therebychanging the capacitance between the inner and outer conductive layers6, 8. In effect, the fabric compression sensor 1 acts like a variablecapacitor when an impact event occurs. Similarly, no data is stored inthe device memory 14 until an impact is detected. This enables theprocessor 13 within the impact detection device 3 to perform high speedsampling tasks relative to the processing power of the device 3 as wellas minimise power consumption of the impact detection device 3. Aspreviously mentioned, the outer conductive layer 8 is electricallyconnected to ground 15 and the inner conductive layer 6 is connected tothe electronic circuitry within the impact detection device 3 to providean analogue signal input, representative of a change in capacitivecoupling between the inner and outer conductive layers 6, 8 due to animpact being detected.

With reference to FIG. 6, all timing and clocking for the impactdetection device 3 is derived from a crystal oscillator 16. The clockingsignal is used to clock the processor 13 as well driving the capacitivefabric compression sensor(s) 1. Using this type of system clocking isalso used to drive the analogue to digital converter (ADC) 19 and thesignal peak to peak measuring algorithm derived from the processor 13 tobe applied to the sensed input signal from the fabric compression sensor6. This then provides a means synchronising the sensed impact signal 9with a processor derived test signal in order to reduce processing powerrequirements and enable a low power processing solution to be used.

The analogue signal input is a low frequency signal and as such, thesignal input amplifier 17 exhibits a low pass frequency response. Thefabric compression sensor(s) 1 uses an AC signal generated by the impactsensing and processing device 3 and is driven within a controlled highoutput reference resistance (R_(ref)) 18 of between 10 kOhms to 100kOhms. The high output reference resistance 18 is equal in magnitude tothe impedance of the capacitive fabric compression sensor (s) 1 at thedrive signal impedance as:R_(ref)≈1/(ωC)where ω is the AC signal frequency (rad/s) and C is the capacitance ofthe capacitive fabric compression sensor (F).

The capacitive fabric compression sensor(s) 1 acts as a variablecapacitor which has one terminal (outer layer 8) coupled to AC ground 15and the other terminal (inner layer 6) attached to the high impedanceresistor 18 to provide an analogue input drive signal. The AC ground 15is the common mode point of the analogue input drive signal coupledthrough the resistor 18 within the impact sensing and processing device3. The AC signal between the high impedance AC signal and the variablecapacitor varies with the change in distance between the inner and outerconductive layers 6, 8 due to the deformation or compression of thenon-conductive layer 7 caused by a detected impact. The AC signalamplitude is sampled by the microcontroller 13 within the impactdetection device 3 to provide a sensed impact waveform. A typical outputof the sensed impact waveform is shown in FIG. 5 whereby the velocity ofthe sensed impact rapidly decreases over time. This enables the initialback face velocity 30 to be determined, the time for the projectile 12to come to rest 31 as well as the projectile rebound velocity 32 overtime.

The impact detection device 3 is a low power device that is powered bybatteries (not shown) and can be switched on using a manual switch (notshown) located on the device 3. Alternatively, the impact detectiondevice 3 can be turned on automatically when the impact detection device3 receives impact detection signals (when the capacitive couplingbetween the inner and outer conductive layers 6, 8 change), as a resultof the non-conductive layer 7 being deformed or compressed due to animpact on the impact surface 2. Each of these “turn-on” configurationscan be set at the time of manufacture or alternatively at a later stageusing the third party system (not shown) and software to interface withthe portable impact detection and sensing device 3.

The impact detection circuit uses an operational amplifier 17 withfeedback to filter out any input noise signals whilst at the same timedetecting a sensed impact signal from the conductive thread 9 attachedto the inner conductive layer 6. This analogue input signal is thenconverted to a digital signal by the ADC 19 before being processed bythe microcontroller 13. Impact sensing is performed by using themicrocontroller crystal 16 to provide a sinewave reference source signaland driving one of the inner conductive fabric sensing layer 6 through alarge resistance 18, such as 100 kOhms, whilst the outer conductivefabric sensing layer 8 is connected to the AC ground 15. Hence, thechange in the capacitive coupling between the inner and outer conductivelayers 6, 8 will alter the peak to peak sinewave signal input to theresistor 18. This sinewave signal provides an input to themicrocontroller 13 to drive the microcontroller 13 and to enablesynchronous sampling to be undertaken by the on-board ADC 19. Softwareresiding within the microcontroller 13 performs peak to peak analysis onthe received sinewave signal input to remove any DC signals which willoccur due to initial garment fitting and background related noise.

The impact detection circuit can alternatively have an analogue signalinput generated by a waveform source 26 such as a pulse width modulator(PWM). The analogue signal output from the signal source is to providean AC reference source for driving one of the inner conductive fabricsensing layers 6 through high output reference resistance (R_(ref)) 18of between 10 kOhms to 100 kOhms whilst the outer conductive fabricsensing layer 8 is connected to the AC ground 15. Hence, the change inthe capacitive coupling between the inner and outer conductive layers 6,8 will alter the amplitude of the AC signal input into the amplifier 28.The signal is then passed through a rectifier 27 which converts the ACsignal into a DC signal before being input into a low pass filter 25.The low pass filter 25 removes the effects of noise before the signal isinput into the ADC 19 which samples the signal.

Once these signals and other sensor inputs are determined the change incapacitive coupling between the inner and outer conductive layers 6, 8is used to calculate the voltage change between the two conductivelayers 6, 8. Using this data, a number of software algorithms are usedto determine the change in distance between the inner and outerconductive layers 6, 8 as a result of an impact being detected on theimpact surface 2. The time taken from when an impact is first detecteduntil the rate of change of capacitive coupling reaches zero is measuredand stored in memory 14. The speed of impact is able to be determined byapplying the formula:

${Speed} = \frac{\begin{matrix}{{Change}\mspace{14mu}{in}\mspace{14mu}{distance}\mspace{14mu}{between}} \\{{the}\mspace{14mu}{inner}\mspace{14mu}{and}\mspace{14mu}{outer}\mspace{14mu}{conductive}\mspace{14mu}{layers}}\end{matrix}\mspace{14mu}}{{Time}\mspace{14mu}{period}\mspace{14mu}{in}\mspace{14mu}{which}\mspace{14mu}{change}\mspace{14mu}{occurred}}$

This data is either stored in memory 14 within the impact detectiondevice 3 for transmission or communication via the communications port20 to a third party system (not shown) at a later date. Alternatively,the data can transmitted, preferably wirelessly using a radiotransmitting device (not shown), in real time to the third party deviceto be logged and analysed. This can be achieved by the user interfacingwith the impact detection device 3 over communications link 20 using asoftware program residing in the third party system. Hence, thecommunications link can be provided by any form of communications meansincluding but not limited to a wired connection, fibre optic, magneticcoupling, short or long range radio devices and a satellite link. Thesoftware system can activate the data download from the impact detectionand processing device 3 to the third party system to enable the thirdparty system to be used to format, view and analyse the sensed impactdata.

Data Processing Circuitry

FIGS. 4, 6 and 7 show block diagrams of the processing circuitry used toreceive the sensed impact data from the signal inputs received from thefabric compression sensors 6, 8. The circuitry is driven by the softwareresiding in the microcontroller 13 using time domain filteringtechniques coupled with frequency locked loop computational algorithmsto convert analogue sensed capacitive coupling variation signals intouseable and meaningful digital formats for storage and/or output to athird party system. The third party system (not shown) subsequentlyconverts the digital data to a numerical and graphic output displaydevice for analysis and review by a professional for example.

Optional Features

The impact sensing and detection system of the present invention can beintegrated with other sensing systems to capture a user's bio-mechanicaldata by monitoring the user's heart rate and respiratory rates forexample. This would require additional sensors to monitor the user'svital signs to be attached to or incorporated within the user'sclothing. Alternatively, the additional sensors and sensing electronicscan be incorporated into or attached to a base layer of clothing suchthat the base layer of clothing lies against the user's skin. Theaddition of different sensor types would provide a more extensivedetermination to be made of the effects of the impact on a user.Furthermore, FIG. 8 shows a garment 40 worn by an individual thatincorporates sections of compression sensors 1 can be attached to orincorporated within the garment 40 to detect and monitor impacts thatmay occur at or in close proximity to the user's vital signs as well asa number of physiological areas of interest. By way of example, thegarment 40 has a left side 41 and a right side 42 and the compressionsensors 1 have been located in positions such that the left side 41 ofthe garment 40 is a mirror image of the right side 42 of the garment 40.The compression sensors 1 have been positioned in a number ofphysiological areas of interest that may include, but are not limitedto: the left and right heart area 43, 44, in close proximity to themid-line of the garment 40; the left and right lung 45, 46; the left andright sides of the lower abdomen 47, 48; the left and right sides of theback (not seen); and the left and right side areas 49, 50. Furthermore,by incorporating one or more compression sensors 1 into a helmet to beworn by an individual, any impacts on the individual's head can bedetected and monitored.

Examples of other sensors and features that can be monitored are asfollows:

1. Movement measurement devices such as solid state accelerometers,solid state gyroscopes, mechanical vibration switches or piezo-electricmovement detectors.

2. A temperature sensor to measure ambient and body temperature such asthermister or infra-red pickup semiconductor device.

3. Heart rate, respiratory rate monitoring using the capacitivecompression sensors positioned in specific positions against the user'sbody and integrated with sensing electronics embedded within the impactdetection device.

4. Pressure sensors to measure altitude using devices such as piezobridges.

5. A flux gate compass for direction sensing.

6. An integration of the impact detection device with GPS and magneticcompass devices will enable the position and direction of the projectile12 to be predicted thereby enabling other personnel to quickly respondto a potential threat situation.

The impact sensing and detection system of the present inventionprovides a portable lightweight device that can be used in a broad rangeof environments and conditions to provide information and feedback onthe effects of a ballistic and non-ballistic type of impacts on animpact surface and ultimately, the residual effects such an impact mayhave on a user. The portability and usability of the device in a broadrange of environments has been achieved by providing a small lightweightsystem that can be coupled with a processing system that is capable ofdiscriminating between a sensed impact signal and residual backgroundnoise to provide a digital output indicative of a detected impact event.

1. A garment for wearing by a user and arranged to detect an impactcomprising: at least one capacitive fabric compression sensor integralwith said garment being formed by an inner layer and outer layer ofconductive fabric having a compressible, non-conductive material betweeneach of said layers of conductive fabric; said outer layer of conductivefabric enclosing said inner layer of conductive fabric; said outer layerof conductive fabric including an electrical isolation region; and animpact detection device electrically connected to said at least onecapacitive fabric compression sensor, at least in part, via saidelectrical isolation region, and including a detecting circuitconfigured to detect a change in the capacitance of the capacitivefabric compression sensor caused by an impact event on said garment, anda processing circuit for processing the change in capacitance into adigital data format representative of an impact characteristic on saidgarment.
 2. The garment according to of claim 1 wherein said garment issegmented to provide a plurality of detection zones wherein each of saidplurality of detection zones has at least one capacitive fabriccompression sensor integral with or attached to said garment andelectrically connected to said impact detection device.
 3. The garmentaccording to claim 1, wherein said outer conductive layer is coupled toan electrical ground within said impact detection device and said innerconductive layer is coupled to a signal input of said impact detectiondevice.
 4. The garment according to claim 3 wherein said processingcircuit samples the amplitude of said signal input to generate a digitalimpact event related waveform and data representative of said impactevent.
 5. The garment according to claim 1, wherein said innerconductive layer is formed from a stretchable and flexible fabricmaterial.
 6. The garment according to claim 1, wherein said innerconductive layer is formed from a metallised cloth.
 7. The garmentaccording to claim 1, wherein said outer conductive layer is formed froma stretchable and flexible fabric material.
 8. The garment according toclaim 1, wherein said outer conductive layer is formed from a metallisedcloth.
 9. The garment according to claim 1 wherein said compressiblenon-conductive material is formed from a closed cell foam type ofmaterial.
 10. A method of detecting an impact on a garment for wearingby a user, comprising: detecting with a detecting circuit a change incapacitance caused by an impact event of a capacitive fabric compressionsensor integral with the garment; said capacitive fabric compressionsensor being formed by an inner layer and outer layer of conductivefabric having a compressible, non-conductive material between the layersof conductive fabric; said outer layer of conductive fabric enclosingsaid inner layer of conductive fabric; said outer layer of conductivefabric including an electrical isolation region; and processing thechange in capacitance into a digital data format representative of animpact characteristic on the garment.
 11. The method of detecting animpact on a garment according to claim 10 wherein the garment issegmented to provide a plurality of detection zones; wherein each ofsaid plurality of detection zones has at least one capacitive fabriccompression sensor integral with or attached to said garment andelectrically connected to said impact detection device.
 12. The methodof detecting an impact on a garment according to claim 10, where theouter conductive layer is coupled to an electrical ground of thedetecting circuit; and wherein said inner conductive layer is coupled toa signal input of the detecting circuit, at least in part, via anelectrical isolation region of the outer later of conductive fabric. 13.The method of detecting an impact on a garment according to claim 12wherein said processing comprises sampling the amplitude of said signalinput to generate a digital impact event related waveform and datarepresentative of said impact event.
 14. The method of detecting animpact on a garment according to claim 10, wherein said inner conductivelayer is formed from a stretchable and flexible fabric material.
 15. Themethod of detecting an impact on a garment according to claim 10,wherein said inner conductive layer is formed from a metallised cloth.16. The method of detecting an impact on a garment according to claim10, wherein said outer conductive layer is formed from a stretchable andflexible fabric material.
 17. The method of detecting an impact on agarment according to claim 10, wherein said outer conductive layer isformed from a metallised cloth.
 18. The method of detecting an impact ona garment according to claim 10 wherein said compressible non-conductivematerial is formed from a closed cell foam type of material.